| Summary: | Abstract: Estuarine barriers may significantly reduce the upstream migration of diadromous fish species like the European eel (Anguilla anguilla L.). Previous research showed that limited barrier opening during tidal rise was a cost-efficient and effective mitigation option to improve upstream glass eel migration, without significant intrusion of sea water. We optimised this adjusted barrier management to improve eel passage at a three different tidal barriers in Flanders, Belgium, blocking the most important migration routes for glass eel in Flanders. Specifically, three hypotheses were tested. The first hypothesis analysed the impact of the number of barriers opened on the upstream glass eel migration. The second hypothesis evaluated the relation between the size of the barrier opening and glass eel migration. Finally, we tested whether the suggested adjusted barrier management may lead to a significant increase in conductivity. Increased opening of one barrier appeared more efficient than opening several barriers slightly. Conductivity increased during periods of extreme drought and at base flow, but decreased within 24h after the first peak flow. This indicates that adjusted barrier management does not entail salt intrusion, as long as this management is not applied in extremely dry periods. Since the adjusted barrier management is easily implemented and could be applied on numerous tidal barriers, the presented results may contribute to restoration of eel populations worldwide and be of interest to a wide range of river managers and stakeholders.
|
|---|